8 
SIDNEY I. KORNHAUSER 
the formation of the one polar cell, leaving in the egg 2n + X 
chromosomes (five in number), and that such an egg forms a 
male In the larger parthenogenetic eggs no whole X-chromosome 
is extruded in the single polar egg given off, and the egg retains 
2n + 2X chromosomes (six in number) and develops into a 
female. In the spermatogenesis of these forms it was found 
that only one secondary spermatocyte develops, that which 
received the X-chromosome. Thus only two instead of four 
spermatids result from a primary spermatocyte and these are 
Diploid Group . Nale Diploid Group Female 
r PartKiajo^enetic off 1 
L one polar toc^. J 
Partiieno^CTiet-ic 
■produces a Female ParlFenogenetie 
Produces a male 
Anapliase Primary Oocyte 
Degenerates 
jPrimaiy Spermatocyt 
■Ptima^ Spermatocyta 
Secondary Spermatids Sperm. 
Spermatocyte ^ 
TelopKase /5fc\ ! (O o' 
_ 'I 2 -P„WlWy 
Fig. 3. Scheme of Reproduction of Aphids and Phylloxerans 
female-determining spermatozoa. In this case of the phyllo- 
xerans and aphids it would thus appear that maturation is in 
reality controlled by the size or composition of the egg. 
It is rather unfortunate that the rotifers and daphnids are not 
such favorable cytological material as the homopterans for it is 
not at all unlikely that their sexual cycles rest upon a basis 
similar to that above described. In rotifers and daphnids the 
biological conditions are almost identical with those of the aphids 
and phylloxerans. Fertilized eggs give rise only to females, 
